The exact quote is "Consumer Gmail content will not be used or scanned for any ads personalization after this change." I know they still scan my emails, because airbnb reservations will magically pop up on my calendar.

Information about events, flights, parcel tracking, etc. are explicitly provided by email senders for things like automatic calendar integration by the email client. https://github.com/schemaorg/schemaorg

Do you log in to AirBnB using Google credentials? Perhaps they use an undocumented feature to broadcast the dates to GCal without mail harvesting.

Nope, using Facebook credentials. That's definitely a possibility.

Maybe I'm cynical, but whenever I see qualifiers around a verb I get suspicious. Something like "hey, we're not lying when we said we stopped scanning emails for ad purposes, but we are still scanning to improve other Google ecosystems tools like Calendar".

They scan emails. I have had airline ticket reservations that my friends emailed to me added on my Calendar.

Yikes. That would prove it...

It's not exactly a secret: https://support.google.com/calendar/answer/6084018?co=GENIE....